docs: def rollout(self, **kwargs):
          """Generate x for open loop movements.
          """
          if kwargs.has_key('tau'):
              timesteps = int(self.timesteps / kwargs['tau'])
          else: 
              timesteps = self.timesteps
          self.x_track = np.zeros(timesteps)
          
          self.reset_state()
          for t in range(timesteps):
              self.x_track[t] = self.x 
              self.step(**kwargs)
  
          return self.x_track